Method and apparatus for mixing pressure gases particularly for respirators and medical apparatus

ABSTRACT

A method for mixing pressure gases includes directing the gases to be mixed through throttles into a mixing pipe while the gases are maintained under pressures which are adjustable in relation to the ratio of the desired gas mixture and while the sum of the gas pressures is constant and with each gas maintained at a pressure above the critical pressure of the gas. The apparatus for carrying out the method includes an adjustable pressure reducer in each gas line which expand the gases to pressures which are always in the same ratio to each other and additional pressure reducers, arranged in each line, which are interconnected in a manner such that an increase in the pressure at the discharge of one provides a corresponding decrease at the other, and vice versa, and which expand the gases to back pressures which are in the same mixing ratio to each other each at a pressure above the critical pressure and with the sum of the pressures being constant. The passage conduits for the gas also include throttles which discharge into a common line for example, for conducting the gases to a respirator.

Oct. 2, 1973 METHOD AND APPARATUS FOR MIXING PRESSURE GASES PARTICULARLYFOR RESPIRATORS AND MEDICAL APPARATUS 3,493,005 2/1970 Kakegawa 137/100Primary Examiner-William R. Cline An0rneyMcGlew and Toren [75] Inventor:Karl F. Miillering, Lubeck, Germany [73] Assignee: DragerwerkAktiengesellschaft, ABSTRACT Lubeck, Germany A method for mixingpressure gases includes directing [22] Filed, June 29 1970 the gases tobe mixed through throttles into a mixing pipe while the gases aremaintained under pressures [21] App]. No.: 50,795 which are adjustablein relation to the ratio of the desired gas mixture and while the sum ofthe gas pressures 30 F A P 1 t is constant and with each gas maintainedat a pressure 1 Drag pphca y Da a above the critical pressure of the gasThe apparatus for July I, Germany P Carrying out the method includes anadjustable pres sure reducer in each gas line which expand the gases to[5%] U.S.CCII. 137/7, 137/100 pressures which are always in the Sameratio to each [5 Int. G05d 11/03 other and additional pressure reducersarranged in [58] Field of Search 137/7 100 63 R 137 9 l4 I45 each line,WlllCh are interconnected in a manner such I that an increase in thepressure at the discharge of one provides a corresponding decrease atthe other; and [56] References Cited vice versa, and which expand thegases to back pres- UNITED STATES PATENTS sures which are in the samemixin ratio to each other g 3,530,873 9/1970 Arp.. 128/145.6 each at apressure above the critical pressure and with 3,530,872 9/1970 P":l37/99 the sum of the pressures being constant. The passage 3,605,7859/1971 P F 137/101 conduits for the gas also include throttles whichdischarge into a common line for example, for conducting o ens 3,068,87912/1962 Snowman.... 137 100 the gases a resp'rator' 3,273,982 9/1966McDonald 137/7 9 Claims, 1 Drawing Figure 9 I e1 1 l 1 v 7 42 '4 DOUBLE23 24 25 MAGNETIC 8 E1 VALVE g 2 4 I I 2 6 H x 3 1 1 A 40 H6 565 5b /2632 29 28 27 pm CONTROL TmGeLR J 2 I AFETY VALVE PAIENIEB B 3363427CONTROL KARL F. MOLLERING ATTORNEYS INYENTOR.

METHOD AND APPARATUS FOR MIXING PRESSURE GASES PARTICULARLY FORRESPIRATORS AND MEDICAL APPARATUS SUMMARY OF THE INVENTION Thisinvention relates in general to a method and apparatus for mixing gasesand in particular, to a new and useful method and apparatus forcontrolling the feed of two separate gases into a combined deliveryline, for example, for a medical device such as a respirator.

Methods and devices for mixing gas currents are known. One methodcomprises expanding two pressure gases each through a throttle valve anda flow meter in a common waste gas line where the mixing ratio of thegases to be mixed in set in the flow meters. This method has thedisadvantage that the flow meters and the throttle valves must beconstantly checked. in addition, one must make sure that an exactlydetermined pressure is always maintained in the flow meter or thereading of the flow meter will not be correct. In this method, it isthus necessary to ensure the exact maintenance of a certain outletpressure. Another known method includes expanding two pressure gases toatmospheric pressure and then delivering the gases into piston pumpswith a variable stroke volume forforced delivery into an outlet pipe.This method has the disadvantage that it requires a great number ofparts such as piston pumps and drives for the pumps as well as controldevices therefor.

In accordance with the present invention, there is provided a gas mixingmethod which permits the production of a gas mixture of two pressuregases set to a certain ratio and without the disadvantages of the priorart. The rate of flow of each gas may be set to a desired value withsimple means without changing the mixing ratio. The method isparticularly applicable for mixing pressure gases particularly forrespirators and other medical apparatus. The invention comprisesdirecting the gases to be mixed through separate conduits into separatethrottles which discharge into a combined gas conduit in a manner suchthat the pressures are adjustable in the ratio of the desired mixtureand the sum is maintained constant while each of the gases aremaintained at a pressure above the critical pressure of the associatedgas. The method of the invention has the advantage that a gas mixture ofa desired concentration ratio is produced satisfactorily and with simplemeans and this concentration ratio does not change when the rate of flowof the gas varies. The rate of flow and the mixing ratio are determinedby varying the pressures ahead of the throttles.

An apparatus for carrying out the invention includes a gas mixer whichis characterized by an adjustable pressure reducer which expands thepressure gases to pressures which are always in the same pressure ratioto each other and which are arranged in combination with additionalpressure reducers which are connected with each other and which expandthe gases with the same pressure sum to back pressures which are in thesame pressure ratio to each other and which are above the criticalpressure. These pressure reducers are arranged in lines which feedthrough throttles to a combination line for the mixed gas. With such amixer the back pressure of the pressure reducers and thus the rate offlow in the mixer can be set by adjusting the first pressure reducer.The pressure reducers must be so adjusted that their back pressures arealways in the same gases to each other can be achieved by adjusting theother pressure reducers which are connected with each other so that thesum of the back pressures remains constant.

With the mixer of the invention, it is thus possible to set selectivelythe rate of flow and the mixing ratio and each of these adjustments areindependent of each other. The mixer has the additional advantage thatthese selected adjustments are independent of the counter pressure inthe mixed gas pipe. This is due to the fact that the preliminarypressure of the gases to be mixed ahead of the throttles is higher thana critical pressure.

A simple arrangement comprises the use of a pressure reducer whichincludes a diaphragm which is adjustable in a known manner and thediaphragm of the pressure reducer in the line of the other gas isstressed with the back pressure of the first pressure reducer. Thisarrangement has the advantage that in order to set the pressures aheadof the throttles in the associated gas lines, it is only necessary toadjust the residual stress of the control diaphragm of one of thepressure reducers. If the back pressure of this one pressure reducer isvaried in this adjustment, the back pressures of the others arecorrespondingly varied in the same ratio. The apparatus can be sodesigned that a spindle provided with a hand wheel and with an indicatormay be employed for adjusting the residual stress of the controldiaphragm of a single pressure reducer to correspondingly produce anadjustment of the other pressure reducers by a correspondingproportional amount. The indicator is advantageously calibrated inliters per minute gas flow.

The apparatus also includes an additional pressure reducer arranged ineach gas line which are coupled together so that the sum of the backpressures of the reducers is constant with any given adjustment. Inorder to be able to shut off the gas flow completely and to start itagain without changing the basic mixing ratio immediately after openingthe shut off valve, the construction advantageously includes jointlyoperated shut off valves arranged in the gas lines between the pressurereducers and the adjustable throttles.

Accordingly, it is an object of the invention to provide an improvedmethod for mixing pressure gases, particularly for respirators andmedical apparatus which comprises directing the gases through separateflow conduits and through throttles into a combination gas conduit forthe mixed gas while they are maintained at pressures which areadjustable in relation to the ratio of the desired gas mixture and whosesum remains constant and which each gas is maintained above the criticalpressure.

A further object of the invention is to provide a device for mixinggases which includes two separate flow lines for the gases to becombined each having a throttle with a discharge into a combinationconduit for the mixed gas and wherein each line includes a firstpressure reducer, one of the first pressure reducers being adjustableand the other being regulated in accordance with the back pressure ofthe first pressure reducer and a second pressure reducer, the secondpressure reducers being coupled together for combined but oppositepressure adjustment and wherein the first pressure reducers may beoperated to provide for a flow regulation of the gases and the secondpressure reducers may be adjusted and controlled to regulate the mixingratio of the gases.

A further object of the invention is to provide a gas mixing devicewhich is simple in design, rugged in construction, and economical tomanufacture.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of this specification. For a better understanding of the invention,its operating advantages and specific objects attained by its use,reference should be had to the accompanying drawings and descriptivematter in which there is illustrated and described a preferredembodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS The only FIGURE of the drawing is theschematic diagram of an apparatus for mixing pressure gases constructedin accordance with the invention.

GENERAL DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawingin particular, the invention embodied therein comprises an apparatus formixing gases which includes a first conduit 1 for the flow of a gas G1and a second conduit 2 for the flow of a gas G2 to be mixed with eachother and which will flow through the conduits with a pressure of 10excess atmosphere for example through the mixer.

In accordance with the invention, first pressure reducers 3 and 4 arearranged in the respective conduits 1 and 2. The first pressure reducer4 is adjustable by the rotation of an adjustable hand wheel to vary thepressure setting on a diaphragm 4a for controlling the back pressuredelivered to the conduit 6 and this back pressure in the conduit 6 iscommunicated through a connecting line 7 to the control diaphragm 3a ofthe pressure reducer 3 so that the gas delivered to the conduit 9thereby is at a pressure which is proportional to that of the circuit 6.The hand wheel is advantageously provided with indications orcalibrations 5a which may be read by an indicator 5b. This indicationmay be read directly in flow rate, that is, in liters per minute.Another indicator in the form of a manometer 8 is also provided in thegas line 6 and its scale may also be calibrated in liters per minute. Inthe arrangement indicated, it is assumed that the back pressures in theconduits 6 and 9 are equal, but of course, they may be set at anydesired ratio to each other. In accordance with a further feature of theinvention, two additional or second pressure reducers l0 and 11 areprovided in the respective conduits 6 and 9 and each carries anadjusting spindle I2, and 13, respectively, for adjusting diaphragms 10aand 1 1a, respectively. The coupling of the two pressure reducers l0 and11 is so designed that when the back pressure of pressure reducer 10 isincreased the back pressure of pressure reducer 11 will becorrespondingly reduced. The sum of these pressures is maintainedconstant. The pressure reducers 10 and 11 discharge through conduits l5and 16 respectively, to a double magnetic valve or solenoid 17 whichinclude individual valve elements, not shown, arranged in the respectiveconduits l5 and 16 so that these conduits may be shut off or fullyopened in accordance with actuation of the valves together from acontrol 29. The conduits and 16 are provided with throttles l8 and 19,respectively and these throttles discharge into a mixing conduit 21 forthe flow of the combined mixed gas to a respirator in a direction of thearrow 22.

When the pressure reducers 10 and 11 are adjusted by adjustment of thehand wheel 14 the mixing ratio of the gases to each other is varied butthe total flow through the device is not changed. This is also true ifthe pressure at the outlet pipe 21 varies. In this pipe 21 theoverflowing gases are mixed and conducted in the direction of the arrow22 to a respirator (not shown) which is applied to a patient. Thepressure in the outlet pipe 21 can be, for example, 10 cm of watercolumn but it can also vary.

Connected to the pipe 21 are a respirator manometer 23, a safety valve24, and a secondary air valve 25. A bypass pipe 26 connects to anoverpressure safety valve 27 and it in turn is connected to a triggermechanism or assembly 28 having an adjustable hand wheel 28a for settingit at a predetermined actuating amount. When the patient is breathingwith aided respiration an under pressure impulse in the patient producesin a contact free switch (not shown) an electrical impulse which istransmitted to the control unit 29. The control unit 29 transmits theimpulse to the double magnetic valve 17 which is opened.

In controlled respiration the control device 29 can be used to adjustthe frequency and this frequency may be set by adjustment of a handwheel 30. The ratio of the duration of inspiration time to expirationtime can be adjusted with the hand wheel 31. The control device 29 isconnected to a suitable source of current 40 and a transformer 32.

The method of operation of the deivce is as follows:

The rate of flow of the gas G1 and G2 to be mixed with each other is setby means of the hand wheel 5. The ratio of the pressures in th pipes 6and 9 will be the same throughout the operation. The higher thesepressures, the greater the amount which will issue from the throttles 18and 19. The rate of flow can thus be regulated with the hand wheel 5.

The mixing ratio of the gases can be properly regulated with thepressure reducers l0 and 11 by adjusting the hand wheel 14. This is truebecause the gases ahead of the throttles 18 and 19 are each under apressure above the critical pressure so that the pressure in the outletpipe 21 will have no effect on the mixing ratio. The critical pressureratio for diatomic gases is (p /p1 crit. 0.53)

Because of the maximum respiration pressure of p 1.1 at. muB) s 1.1/0.53at 2.08 at.)

As the lower limit is therefore selected (p 21.2at.)

With a corresponding modification of the mixer the pressure reducers l0and 11 can also be arranged ahead of the pressure reducers 3 and 4.

The mixer according to the invention, has the advantage that the gasmixture fed to the patient using a respirator will always contain thesame gas concentration and this gas concentration will be independent ofany counter pressure. The gas concentration is also independent of anycounter pressure. The gas concentration is also independent of the rateof flow so that the variations of the rate of flow have no adverseeffect on the gas concentration. Regardless of how the respiration iseffected, the patient always receives a mixture of the sameconcentration.

In the embodiment represented in the drawing the control diaphragms ofthe pressure reducers and 11 are controlled by adjusting spindles 12 and13 with the interposition of springs (not shown) these adjustingspindles will be shifted jointly. It will also be possible to connectthe control diaphragms of the reducers l0 and 11 by springs and a rockermember (not shown) whose bearings can be displaced in the direction ofthe rocker. By displacing the bearing of the rocker arms of the rockerare changed so that the back pressure of the pressure reducers l0 and 11can be varied in opposite directions, butthe sum of these pressures isconstant.

What is claimed is:

l. A method for mixing pressure gases, particularly for respirators andsimilar medical devices, comprising directing pressure gases to be mixedthrough separate pressure reducers to regulate the rate of flow,adjusting the back pressure of the pressure reducers so that the backpressures are always in the same ratio of pressure to each other,directing the gases through further separate pressure reducers,adjusting the further pressure reducers to expand the gases with thesame pressure sum to back pressures which are in the desired ratio toeach other and which are above the critical pressure, directing thegases through separate throttles and discharging the gases from thethrottles into a combining conduit.

2. A method for mixing pressure gases particularly for respirators andmedical apparatus using a separate conduit for the flow of each gas tobe mixed which includes a first pressure reducer for each conduit withthe pressure reducer of one conduit being adjustable and the pressurereducer of the conduit being regulated by the back pressure of the firstconduit and a second reducer in each conduit having a means foradjusting the pressure of one regulator in a predetermined directionwhile the other is adjusted correspondingly in an opposite direction andalso using a throttle in the conduit through which the gases are passedand discharged to a combination conduit, comprising regulating the flowrate of each gas by adjusting the first pressure reducer and to therebyalso adjust the flow in the other conduit by a predeterminedproportional amount, and regulating the quantities of each gas by thecombined regulation of the second reducers while the sum of thequantities of the gases which move through the conduits are maintainedthe same.

3. A device for mixing pressure gases particularly for respirators andmedical apparatus, comprising a first conduit for the flow of a pressuregas and at least one second conduit for the flow of a second pressuregas, a first pressure reducer in said first and second conduits,adjustment means associated with said first pressure reducer of one ofsaid conduits, means for adjusting the pressure reducer of the other ofsaid conduits by the back pressure of said first pressure reducer ofsaid first conduit, a second pressure reducer in each of said conduits,adjusting means for each of said second pressure reducers in each ofsaid conduits for simultaneously adjusting the pressure of said secondpressure reducer in one of said conduits while the pressure reducer ofthe other conduit is adjusted in an equal but opposite direction,throttle means in said first conduit and said second conduit each havinga discharge, and a combined conduit connected to the discharges of saidthrottle means for receiving the combined gases.

4. A gas mixer, according to claim 3, wherein said first pressurereducers in each conduit expand the gases to pressures which are alwaysin the same ratio to each other, said second pressure reducers expandingthe gases with the same pressure sum to back pressures which are in thesame mixing ratio to each other and above the respective criticalpressure.

5. A gas mixer, according to claim 4, wherein an adjustment means forsaid pressure reducer comprises a rotatable hand wheel and indicatormeans associated with said hand wheel.

6. A gas mixer, according to claim 5, wherein said indicator means iscalibrated in gas flow rate.

7. A gas mixer, according to claim 3, wherein said adjustment means forsaid second pressure reducers comprises a rotatable hand wheel andcoupling means between said hand wheel and said first pressure reducersof each of said conduits providing adjustment of said pressure reducersso that the sum of the back pressures of said reducers is constantduring the adjustment.

8. An apparatus, according to claim 3, including shut off valve meansarranged in each of said conduits between said pressure reducers andsaid throttles.

9. A device, according to claim 8, wherein shut off valve means includesa common electrical control for operating said valve means and a triggermechanism connected to said mixing conduit and responsive to apredetermined pressure in said mixing conduit to actuate said shut offvalves.

1. A method for mixing pressure gases, particularly for respirators andsimilar medical devices, comprising directing pressure gases to be mixedthrough separate pressure reducers to regulate the rate of flow,adjusting the back pressure of the pressure reducers so that the backpressures are always in the same ratio of pressure to each other,directing the gases through further separate pressure reducers,adjusting the further pressure reducers to expand the gases with thesame pressure sum to back pressures which are in the desired ratio toeach other and which are above the critical pressure, directing thegases through separate throttles and discharging the gases from thethrottles into a combining conduit.
 2. A method for mixing pressuregases particularly for respirators and medical apparatus using aseparate conduit for the flow of each gas to be mixed which includes afirst pressure reducer for each conduit with the pressure reducer of oneconduit being adjustable and the pressure reducer of the conduit beingregulated by the back pressure of the first conduit and a second reducerin each conduit having a means for adjusting the pressure of oneregulator in a predetermined direction while the other is adjustedcorrespondingly in an opposite direction and also using a throttle inthe conduit through which the gases are passed and discharged to acombination conduit, comprising regulating the flow rate of each gas byadjusting the first pressure reducer and to thereby also adjust the flowin the other conduit by a predetermined proportional amount, andregulating the quantities of each gas by the combined regulation of thesecond reducers while the sum of the quantities of the gases which movethrough the conduits are maintained the same.
 3. A device for mixingpressure gases particularly for respirators and medical apparatus,comprising a first conduit for the flow of a pressure gas and at leastone second conduit for the flow of a second pressure gas, a firstpressure reducer in said first and second conduits, adjustment meansassociated with said first pressure reducer of one of said conduits,means for adjusting the pressure reducer of the other of said conduitsby the back pressure of said first pressure reducer of said firstconduit, a second pressure reducer in each of said conduits, adjustingmeans for each of said second pressure reducers in each of said conduitsfor simultaneously adjusting the pressure of said second pressurereducer in one of said conduits while the pressure reducer of the otherconduit is adjusted in an equal but opposite direction, throttle meansin said first conduit and said second conduit each having a discharge,and a combined conduit connected to the discharges of said throttlemeans for receiving the combined gases.
 4. A gas mixer, according toclaim 3, wherein said first pressure reducers in each conduit expand thegases to pressures which are always in the same ratio to each other,said second pressure reducers expanding the gases with the same pressuresum to back pressures which are in the same mixing ratio to each otherand above the respective critical pressure.
 5. A gas mixer, according toclaim 4, wherein an adjustment means for said pressure reducer comprisesa rotatable hand wheel and indicator means associated with said handwheel.
 6. A gas mixer, according to claim 5, wherein said indicatormeans is calibrated in gas flow rate.
 7. A gas mixer, according to claim3, wherein said adjustment means for said second pressure reducerscomprises a rotatable hand wheel and coupling means between said handwheel and said first pressure reducers of each of said conduitsproviding adjustment of said pressure reducers so that the sum of theback pressures of said reducers is constant during the adjustment.
 8. Anapparatus, according to claim 3, including shut off valve meaNs arrangedin each of said conduits between said pressure reducers and saidthrottles.
 9. A device, according to claim 8, wherein shut off valvemeans includes a common electrical control for operating said valvemeans and a trigger mechanism connected to said mixing conduit andresponsive to a predetermined pressure in said mixing conduit to actuatesaid shut off valves.